1. Field of Invention
The invention relates to an apparatus for applying glue to regions of paper or plastic webs or paper or plastic web-sections. The apparatus includes a nozzle unit having a plurality of glue outlet openings and glue supply lines and a plurality of glue valves, via which the glue supply lines are provided selectively with glue. Each glue valve includes at least one tappet having a sealing head and at least one counter element, with which the sealing head can make sealing contact. The apparatus also includes a glue chamber, via which the glue is provided. The invention also relates to a method of producing the above-described apparatus for applying glue.
2. Description of the Prior Art
An apparatus of the type mentioned above is described in detail in the patent application DE 103 09 893. In the production of paper sacks, it is necessary to provide different components with adhesive. Initially, a tube is shaped out of a web or a plurality of webs forming a multilayered web, one or more traces of glue being applied in the longitudinal direction to regions of the web that are then overlapped by other regions of the web (so-called tube forming). The webs can be made of paper and/or plastic. The tube formed is separated into tube pieces, on which bottoms are molded subsequently, and adhesive is applied again to parts of these tube pieces for gluing the bottoms. Frequently, starch glue is used as the adhesive. Therefore, the word “glue” is used in place of the word “adhesive” in the following parts of this application without restricting the subject matter of the invention.
DE 103 09 893 suggests the use of apparatuses that apply the glue in the desired format by means of a plurality of glue valves instead of glue application rollers that carry the format-dependent plates and that have been in use for decades. The format, in which the glue is applied, can be influenced by suitably controlling individual valves in terms of time. Such apparatuses often comprise a nozzle unit comprising a plurality of glue outlet openings and glue supply lines for these glue outlet openings. Furthermore, the glue valves, by means of which the glue supply lines and thus the glue outlet openings can be provided selectively with glue, are disposed on this nozzle unit. Moreover, the nozzle unit comprises at least one glue chamber, by means of which glue can be provided. The glue is guided to the glue valves by means of glue lines. Glue can flow from the glue chamber through the valves to the glue outlet openings and thus onto the work piece by opening the glue valves. Each glue valve comprises at least one tappet comprising a sealing head that is alterable in terms of its position. This sealing head cooperates with a counter element. For this purpose, the sealing head can make sealing contact with the counter element so that glue cannot flow past the sealing head and through the counter element. When the sealing contact is lifted, the glue valve opens and the glue can flow into the glue supply line. An apparatus of this type of construction is disclosed in the patent application DE 103 30 751.
The nozzle unit is often of two-piece construction, the glue outlet openings and glue supply lines being usually inserted into a nozzle plate. The nozzle head often supports the glue valves and the glue chamber.
The disadvantage of arrangements disclosed in the prior art is that prefabricated glue valves are arranged on the nozzle unit. For this purpose, the nozzle unit must be provided with different bores for each valve, which bores can initially guide the glue from the glue chamber to the surface of the nozzle unit, on which the glue valve is disposed, and which then guide the glue from the valve to the glue outlet opening/s in question. The insertion of bores into the nozzle unit is always associated with high costs. Prefabricated glue valves are also expensive.